The Battle of Galveston came alive for Bob Gearhart with a dive into 46 feet of visually impenetrable Texas City Channel water.

Surveying, site mapping and dredge scheduling gave way to the acrid smoke of cannon and rifle fire of a surprise attack on Jan. 1, 1863, which for a time, returned the city of Galveston to Confederate control. In the chaos of the following morning, the USS Westfield, flagship of the Union blockade there, ran aground in 7 feet of water near Pelican Spit in Galveston Bay.

As Cmdr. William B. Renshaw prepared to destroy the Westfield rather than allow her to be captured, the side-wheel ferryboat exploded, killing Renshaw and a boat crew assisting him. What hadn't been carried off by the crew before the explosion remained deep in the Texas City Channel.

The passage is deep, but not deep enough for satisfactory international ship navigation. In 2004, the U.S. Army Corps of Engineers announced a

$71 million partnership with the oil and refinery businesses that depend upon a navigable Texas City Channel to deepen it. To ensure the integrity of archaeological preservation, the corps hired a nautical archaeology group from Austin headed by Gearhart, who works with PBS&J , a national engineering, environmental and construction planning company.

Many of the assignments Gearhart has taken on in his 20 years with PBS&J involve disproving the archaeological significance of areas in the way of construction or improvement. Of the five sites with possible historical significance that PBS&J surveyed for the Texas City Channel, four yielded finds, such as a sunken channel buoy and a thick piece of steel cable.

The importance of the fifth was confirmed when a diver in the black water bumped into an 11-foot-long piece of metal with an opening at one end.

On Dec. 10, that piece of metal — a 10,000-pound Dahlgren cannon, one of 1,200 made during the Civil War and one of only 50 recovered — was unveiled at Texas A&M University's Institute of Nautical Archaeology.

"It's the pinnacle for me so far for projects like this," said Gearhart, who is cataloging everything recovered by the Westfield wreck.

"This was the flagship of the Union fleet. The surrender of Galveston Island took place on the Westfield. You think about how the war might have been different had she not run aground," he said. "It's so cool."

The members of Gearhart's team was relatively certain they had located the Westfield as early as 2005. Their plan to recover her permits from the Texas Historical Commission and the U.S. Naval History and Heritage Command . The diving expedition to locate her was made in 2008, Gearhart said. The raising of the cannon Nov. 22 and the recovery of the rest of the salvageable metal followed almost a year of planning for the dredging of the channel by the Army Corps of Engineers, he said. The cost of the archaeological portion of the dredging bill was about $3 million, he said.

What the team found was the metal leftovers of a craft built by tycoon Cornelius Vanderbilt to be a Staten Island Ferry but was instead sold to and armed by the Union with the outbreak of the Civil War.

"There was no part of the hull left, just a scattering of metal artifacts," Gearhart said. "When the ship ran aground, much of the material pertaining to the war was probably taken off. The Confederate Army also salvaged some of the Westfield later in the war because they needed the metal."

After some testing to ensure nothing would be damaged, the team employed a powerful electromagnet with a face 5Â½ feet in diameter to pull up larger metal pieces. The team recovered several thousand artifacts, down to tiny, rust-encrusted nails. Other items included 19 cannon balls and 11 oval-shaped U.S. Army buckles, their lead faces stripped of their brass coating.

"We were surprised and pleased to discover that the firebox was intact," Gearhart said. "The iron grates, side by side, where the coal was shoveled in, were still in place."

The tagging, description and cataloging of each artifact should be completed by the end of January, Gearhart said. The items will all eventually be taken for preservation at the Conservation Research Laboratory at the Institute of Nautical Archaeology in College Station .

"This is a part of history I knew nothing about until we got started," Gearhart said. "I have an appreciation now for the role that the Westfield played in the Civil War. In my experience, this is my best project so far."